Magnetic amplifier system



Jall- 1959 H. A. PERKINS, JR 2,871,442

MAGNETIC AMPLIFIER SYSTEM Filed Nov. 14, 1957 i0 34 3-2 35 I? 4323 Input 2 32 E. 33 Output 2| 9 2 E 42 Q A s c 0 E LP 72 5 Fig.!

a 63 64 65 66 67 68 LQQ ll 3 Q 35 A 432 Inpu? E Outpuf 42 40 4x gr 2| Fig. 2

WITNESSES INVENTOR 4 Hurley A. Perkins, Jr.

M 6- lwa I J? ATTORNEY MAGNETIC AMPLIFIER SYSTEM Harley A. Perkins, In, Baldwin Township, Allegheny County, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application November 14, 1957, Serial No. 696,429

7 Claims. (Cl. 323-89) This invention relates to magnetic amplifiers in general and particularly to magnetic amplifier systems including power supplies.

It is an object of this invention to provide an improved magnetic amplifier system.

It is another object of this invention to provide an improved magnetic amplifier system utilizing a power supply which must furnish only two voltages for all purposes including resetting, gating and non-linear circuits.

Further objects of this invention will become apparent when taken in conjunction with the accompanying drawings. In said drawings, for illustrative purposes only, is shown a preferred form of the invention. In said drawings, the manner in which the windings are wound on the saturable magnetic core members is denoted by the polarity dot convention. That is, current flowing into the polarity dot end of a winding will drive the associated core toward positive saturation. Current flowing out of the polarity dot end of a winding will drive the associated core away from positive saturation.

Figure 1 is a schematic diagram of an improved magnetic amplifier system including the magnetic amplifier and an associated power supply; and

Fig. 2 is a schematic diagram of a magnetic amplifier embodying the teachings of this invention which also may be connected to the power supply illustrated in Fig. l embodying the teachings of this invention.

Referring to Fig. l, the apparatus illustrated comprises, in general, a magnetic amplifier designated generally at 30 and a power supply for said magnetic amplifier designated generally at 100.

The magnetic amplifier 30 comprises a saturable magnetic core member 31 having inductively disposed thereon a reset winding 32 and a gating winding 33. A reset circuit for said magnetic amplifier 30 is connected in series circuit relationship between a terminal 36 and an input terminal and comprisesthe reset winding 32, a rectifier 34 and a rectifier 11. A non-linear circuit comprising a rectifier 21 and a resistor 22 is connected in series circuit relationship between a terminal 37 and ground. The junction of the rectifier 21 and the resistor 22 is connected to the junction of the rectifiers 11 and 34. A gating circuit for the magnetic amplifier comprises the gating winding 33 connected in series circuit relationship with a rectifier 35 between the terminal 37 and an output terminal 43. A non-linear circuit 40 is connected between a terminal 44 and ground. The non-linear circuit 40 comprises a resistor 42 and a rectifier 41, the junction of said resistor 42 and rectifier 41 being connected to the output terminal 43.

The power supply 100 comprises means for applying a suitable alternating-current voltage which may be a transformer, such as the one designated generally at 50, an auto-transformer 60 and a saturable reactor 70. The transformer 50 comprises a magnetic core member 51 having a primary winding 53 and a grounded center- "tap, secondary winding 52. The alternating-current voltage is to be applied or connected to the primary winding nited States Patent 0 See 53. The end leads of the secondary winding 52 are connected to the end terminal 63 and 68 of the autotransformer 60. The autotransformer 60 comprises a magnetic core member 61 having inductively disposed thereon a winding 62 having taps 64, 64, 66 and 67 placed at predetermined intervals between the heretofore mentioned terminals 63 and 68. The terminal 63 is connected to a terminal or bus A. The terminal 64 is connected through a winding 72 of the saturable reactor to a terminal or bus C. The terminal 65 is connected to a terminal or bus B. The terminal 66 is connected to a terminal or bus E. The terminal 67 is connected through a winding 73 of the saturable reactor 70 to a terminal or bus D. The terminal 68 is connected to a terminal or bus F. The saturable reactor 70 comprises a saturable reactor 71 having inductively disposed thereon the windings 72 and 73. A resistive means 74 is connected between the terminals C and D.

The power supply operates in the following manner. The alternating voltage which is applied to the primary winding 53 of the transformer 50 will induce a pair of alternating voltages in the secondary winding 52 on each side of the grounded center tap. As is well known in the art, the voltages induced on the secondary winding 52 will be out of phase with respect to each other and to the grounded center-tap. For purposes of this application, the voltage induced on the side of the secondary winding 52 which is connected to the terminal 63 will be considered to be of the 4 phase. The voltage induced on the portion of the secondary winding 52 connected to the terminal 68 will be considered of the 0 phase.

The voltages of the o and 0 phases as taken from the terminals 63 and 68 of the autotransformer 60 will have a larger value than the voltages taken from the other taps of the autotransformer 60 and will be used for gating and non-linear circuits of the magnetic amplifier 30. As is also Well known in the art, the voltages taken from the taps 64 and 67 of the autotransformer 60 will be larger than the voltages taken from the taps 65 and 66 of the autotransformer 60. Both of the latter two voltages will be applied to the resetting circuits of the magnetic amplifier 30 and other similar magnetic amplifiers.

Considering now the terminals A, B, C, D, E and F of the power supply 100, it will be noted that the voltages at the terminals A, B and C will be of the phase while the voltages at the terminals D, E and F will be of the 0 phase.

A first method of operation for the magnetic amplifier 36 will be now considered. For this first method of operation, the terminal 36 is connected to the terminal B, the terminal 37 is connected to the terminal F and the terminal 44 is connected to the terminal A. On a first half-cycle of the alternating voltage connected to the primary winding 53 of the transformer 50, the voltage at the terminal A will be positive going and will be driving the saturable core reactor 31 toward positive saturation. On this same half-cycle the voltage at the terminal B will be negative going but current passage through the resetting winding 32 will be blocked by the rectifier 34.

On the second half-cycle of the alternating voltage connected to the primary windin 53 of the transformer 50, the voltage at the terminal 37 will be negative going but current passage through the gating winding 33 will be blocked by the rectifier 35. However, on this same second half-cycle the voltage at the terminal 36 will be positive going and current will fiow in the resetting winding 32. driving the saturable magnetic core member 31 toward negative saturation.

The magnitude of the voltages herein described is sufficient to drive the saturable magnetic core member 31 to substantially positive and negative saturation by their application to the gating and resetting windings, respectively. The non-linear circuits 20 and 4t hereinbefore described are well-known to those skilled in the art and are so disposed in relationship to the circuit illustrated in Fig. 1 that they permit the flow of a predetermined magnetizing current to the windings 32 and 33 on the core 31 without any voltage drop, while also providing protection to the magnetic amplifier from excessive current flow.

On the first half-cycle described above, the voltage at the terminal 44 was negative going and current was flowing through the rectifier 41 of the non-linear circuit 40 in the forward direction, the magnitude of said current being limited by the resistor 4-2. Therefore, the magnetizing current delivered to the terminal 37 on this first half cycle was allowed to flow through the gating winding 33, the rectifier 35, and the rectifier 41 in the reverse direction. On the second half-cycle described above the voltage at the terminal 37 was negative going and current was flowing from ground through the rectifier 21 of non-linear circuit 20, the magnitude of said current being limited by the resistor 22. Therefore, current was allowed to fiow from the terminal 36 through the gating winding 32, the rectifier 34 and the rectifier 21 in the reverse direction.

The magnetic amplifier 30 will continue to cycle between positive and negative saturation with no output at the terminal 43 until an input signal of the proper phase and of a predetermined magnitude is applied to the input terminal 10. The signal applied to the input terminal will block the flow of current through the rectifier 34 and will determine the amount of reset accomplished on the resetting half-cycle. On a succeeding half-cycle, since the saturable magnetic core 31 is not at negative saturation, there will be an output from the gating winding 33 through the rectifier 35 to the terminal 43. The amount of this output will be principally determined by the magnitude of the signal applied to the input terminal 10.

If an output of the opposite phase is desired from the magnetic amplifier 30 then the terminals 36, 37 and 44 are connected to like terminals of the power supply 100 having the same magnitude of voltage which, however, are of the opposite phase. In this situation, an opposite phase of input signal is also required.

For certain applications, it is desirable that a number of the magnetic amplifiers of the type illustrated in Fig. 1 be cascaded. Theoretically, if perfectly square, hysteresis loop core materials and zero reverse leakage rectifiers are used in magnetic amplifier systems incorporating voltage reset means, the output from the saturable reactors contained therein is a function of the amount of the reset applied to the saturable reactors by the reset windings. A signal introduced into the input of such a cascaded amplifier system will tend to block the reset voltage of the first stage at the reset rectifier, if the magnitude of the input signal, at any particular time, is larger than that of the reset voltage. Therefore, the reset is removed from the saturable magnetic core of the first stage and on the next half-cycle the gating supply of voltage will produce a full output when the output winding turns are just sufiicient to drive the magnetic core through a flux change of twice the saturation flux density with a given gating supply of voltage. By proper design,

the output from the first stage of a cascaded magnetic amplifier system can be made large enough in magnitude to block the reset voltage of the second stage. By so doing, there is a full output, subject to the conditions above, from the second stage in the same manner as from the first stage. This is repeated through N stages of the cascaded magnetic amplifier system.

Practically, perfect square hysteresis loop magnetic core materials can be approached but never achieved with present magnetic core fabrication methods and I processes. The residual flux density of present magnetic core material is less than the maximum flux density. Therefore, the saturable reactor or the saturable magnetic core of the first stage magnetic amplifier is not completely saturated for an entire gating half cycle. Rectifiers with zero reverse leakage are also not available. This reverse leakage of the rectifiers further modi fies the state of flux in the magnetic core during a reset half-cycle. As a result, a signal applied to the input of a cascaded amplifier system will produce at the output of the first stage a conduction angle that is less than the conduction angle of the input signal. An additional attenuation in conduction angle is added by each stage, so that after a sufficient number N stages an output might not appear at all.

The problem discussed above may be overcome by applying a voltage of a special waveform to the reset windings of the cascaded magnetic amplifiers. Provision for this is made in a power supply 1% where the voltages from the terminals 64 and 67 of the autotransformer 61 are applied-to the terminals C and D through the windings 72 and 73 inductively disposed on the saturable magnetic core 71 of the saturable reactor '70. For a more detailed description of the action of the special waveform resetting voltages derived from the terminals C and D of the power supply on several cascaded stages of magnetic amplifiers similar to the magnetic amplifier 30, reference is made to a copending application Serial No; 640,006, entitled Magnetic Amplifier Systems, filed February 13, 1957, and assigned to the same assignee as this application.

For that particular mode of operation of the magnetic amplifier 30, with the connections of the terminals 37 and 44 to the terminals F and A as hereinbefore described, the terminal 36 would be connected to terminal C of the power supply 100 in order to furnish the proper phase of resetting voltage. As was described hereinbefore, for a change in the phase of the output of the magnetic amplifier 30 the terminals 36, 37 and 44 must be changed to terminals of the power supply 100 furnishing a like magnitude but opposite phase as heretofore connected. The change for the terminal 36 when a special waveform of reset voltage is desired would be from the terminal C to the terminal D.

Referring to Fig. 2 there is illustrated another embodiment of the teachings of this invention, in which like components of Figs. 1 and 2 have been given the same reference characters. Since the same power supply 100 will be used for the apparatus for the magnetic amplifier 39 illustrated in Fig. 2, the drawing of the power supply 106 is not repeated. The main distinction between the magnetic amplifier 30 illustrated in Figs. 1 and 2 is that in Fig. 2 the rectifier 34 has been omitted and the non-linear circuit 20 comprising the rectifier 21 and the resistor 22 has been redisposed in the reset circuit to allow resetting of the saturable magnetic core 31 only by an input signal applied to the terminal 10.

Assuming that the terminals 37 and 44 are again connected to the terminals F and A, respectively, of the power supply 100, the operation of the magnetic amplifier 30 will be the same when the voltages are applied to the gating winding 33 and the non-linear circuit 40. However, since no reset voltage is being applied to the reset winding 32, the saturable magnetic core 31 will be reset only upon the application of a signal to the terminal 10 of the proper phase and of the predetermined magnitude. The phase for the input signal must be out of phase with the gating voltage applied to the terminal 37. Resetting of the saturable magnetic core member 31 will be held to this particular time since the non-linear circuit 20 is operative to allow current flow through the rectifier 21 in a reverse direction only when the voltage applied to the terminal 37 is negative going.

The output at the terminal 43 from the magnetic amplifier 30 will be determined by the magnitude of the input to the terminal 10. When no input signal is present there will be a full output at the terminal 43. When a full predetermined magnitude of input signal is present at the terminal there will be no output in a' predetermined half-cycle at the terminal 43.

This invention as illustrated in the embodiments described in Figs. 1 and 2 features a simplification in circuitry which results in fewer power supply components and reduces the number of power supply voltages which must be made available. Outstanding is the elimination of the direct-current bias usually supplied to nonlinear circuits by substituting and connecting the alternating-current voltages hereinbefore described to provide current for the non-linear device when the alternating current-voltages are negative going. Also, the alternating-current voltages hereinbefore described, when positive going as a bias voltage to the non-linear circuits, provides blocking voltages whereby the rectifier in the gating circuit of the magnetic amplifiers allows the special waveforms of reset voltages to be used, when cascading a number of the magnetic amplifier stages, without introducing other forms of compensation for induced voltages that were required in the prior art use of special waveform power supplies. Rectifiers are eliminated from the power channels and fewer conductors or buses are required thereby also requiring fewer power terminals for the magnetic amplifiers to be connected to the power supplies.

In conclusion, it is pointed out that while the illustrated examples constitute practical embodiments of my invention, I do not limit myself to the details shown, since modifications of the same may be varied without departing from the spirit and scope of this invention.

I claim as my invention:

1. In a magnetic amplifier system, in combination; a power supply; a magnetic amplifier having a reset and a gating circuit; said power supply comprising an autotransformer and means for applying a source of alternating-current voltage to said autotransformer; said reset circuit comprising a reset winding inductively disposed on a saturable magnetic core member and connected in series circuit relationship with a first non-linear circuit means; said gating circuit comprising a gating winding inductively disposed on said saturable magnetic core member and connected in series circuit relationship with rectifier means and a second non-linear circuit; said autotransformer having taps at predetermined intervals whereby voltages of like magnitudes but opposite phases are available on each side of said autotransformer; circuit means connecting a first alternating-current voltage of a first phase from said autotransformer to said gating circuit and said first non-linear circuit; circuit means connecting a second alternating-current voltage of a second phase from said autotransformer to said reset circuit.

2. In a magnetic amplifier system, in combination; a power supply; a magnetic amplifier having a reset and a gating circuit; said power supply comprising an autotransformer and means for applying a source of altermating-current voltage to said autotransformer; said reset circuit comprising a reset winding inductively disposed on a saturable magnetic core member and connected in series circuit relationship with rectifier means and a first non-linear circuit means; said gating circuit comprising a gating winding inductively disposed on said saturable magnetic core member and connected in series circuit relationship with rectifier means and a second non-linear circuit; said autotransformer having taps at predetermined intervals whereby voltages of like magnitudes but opposite phases are available on each side of said autotransformer; circuit means connecting a first alternating-current voltage of a first phase from said autotransformer to said gating circuit and said first nonlinear circuit; and circuit means connecting a second alternating-current voltage of a second phase from said autotransformer to said reset circuit.

, 3. In a magnetic amplifier system, in combination; a power supply; a magnetic amplifier having a reset and a gating circuit; said power supply comprising an autotransformer and means for applying a source of alternetting-current voltage to said autotransformer; said reset circuit comprising a reset winding inductively disposed on a saturable magnetic core member and connected in series circuit relationship with rectifier means and a first non-linear circuit means; said gating circuit comprising a gating winding inductively disposed on said saturable magnetic core member and connected in series circuit relationship with rectifier means and a second non-linear circuit; said autotransformer having taps at predetermined intervals whereby voltages of like magnitudes but opposite phases are available on each side of said autotransformer; circuit means connecting a first alternating-current voltage of a first phase from said autotransformer to said gating circuit and said first nonlinear circuit; circuit means connecting a second alternating-current voltage of a second phase from said autotransformer to said reset circuit; and circuit means connecting a third alternating-current voltage of said first phase from said autotransformer to said second nonlinear circuit.

4. In a magnetic amplifier system, in combination; a power supply; a magnetic amplifier having a reset and a gating circuit; said power supply comprising an autotransformer and means for applying a source of alternating-current voltage to said autotransformer; said reset circuit comprising a reset winding inductively disposed on a saturable magnetic core member and connected in series circuit relationship with a first nonlinear circuit means; means for applying an input signal to said reset circuit whereby said second alternatingcurrent voltage is blocked in said reset circuit, said gating circuit comprising a gating winding inductively disposed on said saturable magnetic core member and connected in series circuit relationship with rectifier means and a second non-linear circuit; said autotransformer having taps at predetermined intervals whereby voltages of like magnitudes but opposite phases are available on each side of said autotransformer; circuit means connecting a first alternating-current voltage of a first phase from said autotransformer to said gating circuit and said first non-linear circuit; circuit means connecting a second alternating-current voltage of a second phase from said autotransformer to said reset circuit; and circuit means connecting a third alternating-current voltage of said first phase to said second non-linear circuit.

5. In a magnetic amplifier system, in combination; a power supply; a magnetic amplifier having a reset and a gating circuit; said power supply comprising an autotransformer and means for applying a source of alternating-current voltage to said autotransformer; said reset circuit comprising a reset winding inductively dis posed on a saturable magnetic core member and connected in series circuit relationship with a first nonlinear circuit means; means for applying an input signal to said reset circuit whereby said saturabie magnetic core is driven away from positive saturation; said gating circuit comprising a gating winding inductively disposed on said saturable magnetic core member and connected in series circuit relationship with rectifier means and a second non-linear circuit; said autotransformer having taps at predetermined intervals whereby voltages of like magnitudes but opposite phases are available on each side of said autotransformer; circuit means connecting a first alternating-current voltage of a first phase from said autotransformer to said gating circuit and said first non-linear circuit; and circuit means connecting a second alternating-current voltage of a second phase from said autotransformer to said reset circuit.

6. In a magnetic amplifier system, in combination; a power supply; a magnetic amplifier having a reset and a gating circuit; said power supply comprising an autotransformer and means for applying a source of alternating-current voltage totsaid autotransformer; said reset circuit comprising a reset Winding inductively disposed on a saturable magnetic core member and connected in series circuit relationship with rectifier means and a first non-linear circuit means; said gating circuit comprising a gating winding inductively disposed on said saturable magnetic core member and connected in series circuit relationship with rectifier means and a second non-linear circuit; said autotransformer having taps at predetermined intervals whereby voltages of like magnitudes but opposite phases are available on each side of said autotransformer; circuit means connecting a first alternating-current voltage of a first phase from said autotransformer to said gating circuit and said first nonlinear circuit; and circuit means connecting a second alternating-current voltage of a second phase from said autotransformer through a saturable reactor to saidreset circuit.

7. In a magnetic amplifier system, in combination; a power supply; a magnetic amplifier having a reset and a gating circuit; said power supply comprising an autotransformer and means for applying a source of alternating-current voltage to said autotransformer; said reset circuit comprising a reset winding inductively disposed on a saturable magnetic core member and connected in series circuit relationship with rectifier means and a first non-linear circuit means; means for applying an input signal to said reset circuit whereby said second alternating-current voltage is blocked in said reset circuit; said gating circuit comprising a gating winding inductively disposed on said saturable magnetic core member and connected in series circuit relationship with rectifier means and a second non-linear circuit; said autotransformer having taps at predetermined intervals whereby voltages of like magnitudes but opposite phases are available on each side of said autotransformer; circuit means connecting a first alternating-current voltage of a first phase from said autotransformer to said gating circuit and said first non-linear circuit; and circuit means connecting a second alternating-current voltage of a second phase from said autotransformer through a saturable reactor to said reset circuit.

No references cited. 

